Communication through “language” (verbal communication) is used most often as existing communication. The communication through language is superior in information transmission. For example, conveying feelings to residents located indoors is possible by way of the communication through language. On the other hand, it is not preferable in terms of crime prevention or public morals for the feelings of persons located indoors to be overheard outdoors.
Further, in recent years, awareness of crime prevention has progressed along with the decline of local community, and various techniques related to home security such as introduction of surveillance cameras have been proposed. For example, a system in which, if an abnormality is detected by a sensor, abnormal information is transmitted to a center apparatus of a security company, and a sound or a video is output from a door intercom to intimidate a burglar, or a notification of the abnormal situation is given to a neighboring resident is disclosed in Patent Literature 1.